The head of the Biology Department at Indiana University South Bend, Professor Thomas M. Clark, recently published in 2017 a lengthy “systematic review, meta-analysis, and narrative summary of effects of cannabis use on mortality are performed.”
The bottom line from the 53 page document titled “Cannabis use is associated with a substantial reduction in premature deaths in the United States” is:
"Cannabis use prevents thousands of premature deaths each year, and Cannabis prohibition is revealed as a major cause of premature death in the U.S."